The term Jacob's staff, also cross-staff, a ballastella, a fore-staff, or a balestilha, is used to refer to several things. This can lead to considerable confusion unless one clarifies the purpose for the object so named. The two most frequent uses are:
- in astronomy and navigation for a simple device to measure angles, later replaced by the more precise sextants;
- in surveying for a vertical rod that penetrates the ground and supports a compass or other instrument.
Read more about Jacob's Staff: Astronomy and Navigation, Surveying
Famous quotes containing the words jacob and/or staff:
“I was not unemployed in my profession by the late John Jacob Astor; a name which, I admit, I love to repeat, for it hath a rounded and orbicular sound to it, and rings like unto bullion.”
—Herman Melville (1819–1891)
“Each one threw down his staff, and they became snakes; but Aaron’s staff swallowed up theirs.”
—Bible: Hebrew, Exodus 7:12.